Suitability to a Free Range Environment
Don't automatically discount the white breeds. Most pastured pigs produced on a commercial scale are white. They often don't look too white (and the pig in the picture is a perfect example) but that is because they have a good coating of dust and dirt on their skin to protect them from the sun.
The argument that white sows will suffer from sunburn and get skin cancer is one sided. It is used to justify keeping sows in stalls and sheds. White pigs that have been born outdoors will cope very well with the environment.
However, it is not advisable to take a white pig that has been raised indoors and put it outside. It will need a long time to adapt to a natural environment.
The question about which breed tastes best is a common one. The environment in which the pig is raised will have the biggest influence on flavour. Rare breeds of pigs are usually kept by small producers on free range farms and this would explain why people notice such a difference in taste compared to pork produced intensively. White crossbred pigs will also taste exceptional when raised under outdoor conditions.
Flavour is all about how the pork is produced!